Preparation and application of zinc dihydrogen phosphate_industrial additives


Zinc dihydrogen phosphate is a white triclinic crystal or white solid substance, which is deliquescent and decomposes at 100°C when exposed to water. It contains high levels of free acid and is highly corrosive. It is used as an analytical reagent and preservative and is also used in the glass and ceramic industries.


Wang Rui et al. synthesized organic phosphonic acid corrosion inhibitors using tetraethylene pentamine, formaldehyde and phosphorous acid as raw materials, compounded with zinc dihydrogen phosphate, and investigated the relationship between organic phosphonic acid corrosion inhibitors and zinc dihydrogen phosphate. The influence of mass ratio, compound system addition amount, corrosion time, corrosion temperature and system pH value on the corrosion inhibition effect of the compound system. The results show that the corrosion inhibition rate of organic phosphonic acid corrosion inhibitors alone is 76.92%. After compounding organic phosphonic acid corrosion inhibitors and zinc dihydrogen phosphate at a mass ratio of 3:1, the corrosion inhibition rate can reach 96.59%. The compound corrosion inhibitor also has the advantages of low dosage, good stability, good temperature resistance and salt resistance.


Preparation of zinc dihydrogen phosphate crystal:

1. Add high-purity zinc oxide into the enamel reactor, add deionized water, and stir into a paste with a solid content of 55-65%; the high-purity zinc oxide refers to a content of 99.99%. Zinc oxide antioxidant 4020 containing Fe, Cu, Ni, Cr, Co, Mn, Ti, V and Pb content less than 0.5ppm;

2. Add the high-purity reagent phosphoric acid with a concentration of 85% into the enamel reactor, add deionized water to prepare a phosphoric acid with a concentration of 75%, raise the temperature to 85-95°C, and slowly stir with sufficient stirring. Add the zinc oxide paste prepared in step 1.2) for reaction. Keep the reactant solution clear and transparent throughout the reaction process. When the pH value is 1 to 2, a zinc dihydrogen phosphate solution is obtained. The high-purity reagent phosphoric acid refers to the content. Phosphoric acid with a content of 99.99%, and metal element impurities Fe, Cu, Ni, Cr, Co, Mn, Ti, V, and Pb are all less than 0.3ppm;

3. Heat the zinc dihydrogen phosphate solution to 135~140℃ and concentrate the reactant to a specific gravity of 1.66~1.70. Put the material into a cooling container. When the temperature drops to 70~75℃, stir and place in the cooling container. Add cooling water to cool the crystallization to room temperature to obtain zinc dihydrogen phosphate crystal;

4. Put the zinc dihydrogen phosphate crystal into a centrifuge to separate the liquid from solid, spin dry and set aside.


Zinc dihydrogen phosphate can be used to prepare zinc metaphosphate as an optical glass additive. Put the dried zinc dihydrogen phosphate crystals into a silica ceramic crucible, put the silica ceramic crucible into a calcining furnace, and calcine at a temperature of 950 to 1350°C for 3 to 5 hours to form a glassy partial crucible. Zinc phosphate flows into a container filled with cooling water to form glass slag-like zinc metaphosphate; the main content of silica in the silica ceramic crucible is 99.99%, including metal element impurities Fe, Cu, Ni, Cr, The contents of Co, Mn, Ti, V and Pb are all less than 0.3ppm.

CN201910394813 discloses a metal treatment agent for the surface treatment process of high-anti-corrosion finished auto parts products, which is composed of the following raw materials: boric acid, phosphoric acid, triethanolamine, sericin, vinyltrimethoxysilane, urotropine, and aminotrimethylidene Phosphonic acid, zinc dihydrogen phosphate, tartaric acid and ferrous oxalate; the mass fractions of each raw material are: 20-22 parts of boric acid, 18-20 parts of phosphoric acid, 6-8 parts of triethanolamine, 2-6 parts of sericin, 3-7 parts of vinyltrimethoxysilane, 1-3 parts of methenamine, 1-3 parts of aminotrimethylenephosphonic acid, 2-4 parts of zinc dihydrogen phosphate, 2-8 parts of tartaric acid, 8-8 parts of ferrous oxalate 12 servings. The formula of the invention is simple and practical. The metal workpiece is invaded into the phosphating solution and can be deposited on the surface at normal temperature to form a water-insoluble crystalline phosphate conversion film. The film layer has a microporous structure, is firmly combined with the substrate, and has good properties. Adsorption, lubricity, corrosion resistance, non-adhesion to molten metal and high electrical insulation.

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